JP2018132777A - Optical modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical modulator having a reduced chip width, which has a light-receiving element in each of a plurality of modulation parts.SOLUTION: The optical modulator includes a substrate 1 having an electro-optic effect, an optical waveguide 2 formed on the substrate 1, a modulation part M for modulating light waves propagating in the optical waveguide 2, and a light-receiving element 4 for detecting the light waves propagating in the optical waveguide 2. The modulation part M includes a first modulation part M(#1) and a second modulation part M(#2), each modulating optical waves branched from input light. The light-receiving element 4 includes a light-receiving element 4(#1) corresponding to the modulation part M(#1) and a light-receiving element 4(#2) corresponding to the modulation part M(#2). The light-receiving element 4(#1) and the light-receiving element 4(#2) are arranged at positions deviated from each other in the propagation direction of light by a distance equal to or more than one light-receiving element.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an optical modulator, and more particularly to an optical modulator having a plurality of light receiving elements corresponding to a plurality of modulation units.

  As the speed and capacity of optical communication systems are increasing, the performance and density of optical modulators used therein are increasing. In addition, with the demand for miniaturization of optical modulators, miniaturization of substrates constituting the optical modulators is also being promoted. However, since high performance, high density, and miniaturization of the optical modulator are contradictory requirements, a contrivance for achieving both of these is required.

The following invention is proposed regarding such an optical modulator.
For example, Patent Document 1 discloses that light that travels through an optical waveguide is reflected by a reflection film on the bottom surface of the reflection groove and is directed upward by reflecting the light emitted from the optical waveguide and entering the reflection groove. An optical modulator having a structure in which light is received by a light receiving element fixed to the surface of the light is disclosed.
For example, in Patent Document 2, a light receiving element is arranged so as to straddle an output waveguide that constitutes a Mach-Zehnder type waveguide, and receives two radiated lights emitted from a multiplexing part of the Mach-Zehnder type waveguide. And an optical modulator having a structure in which two or more light receiving portions are formed apart from each other on one light receiving element substrate.

Japanese Patent Laying-Open No. 2015-18193 JP2015-194517A

FIG. 1 is a plan view for explaining an optical modulator according to Conventional Example 1. FIG.
The optical modulator according to Conventional Example 1 includes a first modulation unit M (# 1) and a second modulation unit M (# 2) that modulate each of the light waves branched from the input light. Each modulation unit M is configured using an optical waveguide 2 formed on a substrate 1 having an electro-optic effect, and a control electrode 3 for controlling a light wave propagating through the optical waveguide 2 with a control signal. The control electrode 3 includes an RF electrode 3a to which an RF signal (modulation signal) as a kind of control signal is applied, and DC electrodes 3b and 3c to which a DC signal (bias voltage) as a kind of control signal is applied. Is done.

  The optical waveguide 2 constituting the modulation section M has a structure in which a sub Mach-Zehnder type waveguide is arranged in a nest type in the arm part of the main Mach-Zehnder type waveguide. The light wave (signal light) modulated by the modulation unit M is guided to the outside of the substrate through the output waveguide 21 connected to the multiplexing unit of the main Mach-Zehnder type waveguide in the modulation unit M.

  On both sides of the output waveguide 21 of each modulation section M, a radiation light waveguide 22 that propagates radiation emitted from the multiplexing section of the main Mach-Zehnder type waveguide in the modulation section M is provided. The light receiving element 4 is disposed so as to straddle the output waveguide 21 and the radiated light waveguides 22 on both sides thereof. In this example, the light receiving element 4 includes a light receiving element 4 (# 1) for the modulation unit M (# 1) and a light receiving element 4 (# 2) for the modulation unit M (# 2). Each light receiving element 4 has a light receiving portion 41 for receiving a light wave from each of the radiated light waveguides 22, and is fixed to a predetermined position on the substrate 1 with an adhesive 42. .

  In the optical modulator according to Conventional Example 1, the modulation units M are aligned in the length direction (light propagation direction) of the substrate 1 and arranged in the width direction of the substrate 1. Similarly, the respective light receiving elements 4 are arranged in the length direction of the substrate 1 and aligned in the width direction of the substrate 1. As the light receiving element 4, one having a side length of about 0.2 mm to 0.5 mm and a diameter of the light receiving portion 42 of about 30 μm to 150 μm is used. In order to increase the workability of the light receiving element 4 to the substrate 1 and the reliability of bonding, the distance (D11) between the adjacent light receiving elements 4 (# 1) and 4 (# 2) is set to some extent (0. About 1 mm to 0.2 mm). Accordingly, it is necessary to increase the distance (D12) between the optical waveguide 2 on the light modulation region M (# 1) side and the optical waveguide 2 on the light modulation region M (# 2) side. (Chip width W) is a factor that increases.

FIG. 2 is a plan view for explaining an optical modulator according to the second conventional example.
The optical modulator according to Conventional Example 2 includes a first modulation unit M (# 1) and a second modulation unit M (# 2) that respectively modulate light waves obtained by branching input light having a wavelength λ1, and a wavelength λ2. A third modulation unit M (# 3) and a fourth modulation unit M (# 4) are provided for modulating each light wave obtained by branching the input light. Each modulation unit M includes an optical waveguide 2 formed on a substrate 1 having an electro-optic effect, and a control electrode 3 (RF electrode 3a and DC electrodes 3b and 3c) for controlling light waves propagating through the optical waveguide 2 with a control signal. Etc.).

  The optical waveguide 2 constituting the modulation section M has a structure in which a sub Mach-Zehnder type waveguide is arranged in a nest type in the arm part of the main Mach-Zehnder type waveguide. The light wave (signal light) modulated by the modulation unit M is guided to the outside of the substrate through the output waveguide 21 connected to the multiplexing unit of the main Mach-Zehnder type waveguide in the modulation unit M.

  On one side of the output waveguide 21 of each modulation section M, a monitor waveguide 24 that extracts and propagates a part of the light wave propagating through the output waveguide 21 for monitoring is provided. The light receiving element 4 is disposed so as to straddle the monitoring waveguide 24. In this example, as the light receiving element 4, the light receiving element 4 (# 1) for the modulation unit M (# 1), the light receiving element 4 (# 2) for the modulation unit M (# 2), and the modulation unit M (# 3). And a light receiving element 4 (# 4) for the modulation unit M (# 4). Each light receiving element 4 has a light receiving portion 41 for receiving a light wave from the monitoring waveguide 24, and is fixed to a predetermined position on the substrate 1 by an adhesive 42.

  In the optical modulator according to Conventional Example 2, the modulation units M are aligned in the length direction (light propagation direction) of the substrate 1 and arranged in the width direction of the substrate 1. Similarly, the respective light receiving elements 4 are arranged in the length direction of the substrate 1 and aligned in the width direction of the substrate 1. Looking at the modulation units M (# 1) and M (# 2), a sufficient space is provided between the light receiving elements 4 (# 1) and 4 (# 2), so the optical waveguide on the modulation unit M (# 1) side. 2 and the optical waveguide 2 on the modulation unit M (# 2) side can be arranged close to each other. The same applies to the modulation units M (# 3) and M (# 4). However, looking at the modulation units M (# 2) and M (# 3), in order to ensure an interval of about 0.1 mm to 0.2 mm between the light receiving elements 4 (# 2) and 4 (# 3), The distance (D13) between the optical waveguide 2 on the modulation unit M (# 2) side and the optical waveguide 2 on the modulation unit M (# 3) side needs to be separated, and the length in the width direction of the substrate 1 (chip width W) Was a factor that increased.

  The problem to be solved by the present invention is to provide an optical modulator that solves the above-described problems and achieves both high performance, high density, and miniaturization.

In order to solve the above problems, the optical modulator of the present invention has the following technical features.
(1) A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and the optical waveguide An optical modulator comprising: a light receiving element that detects a propagating light wave; and an output for guiding the light wave modulated by the modulation unit to each of the first modulation unit and the second modulation unit. A waveguide and at least one monitor light waveguide for guiding a light wave for monitoring the modulation unit to the side of the output waveguide are provided, and the first modulation unit is used as the light receiving element. A first light receiving element for detecting a light wave propagating through the monitor light waveguide and a second light receiving element for detecting a light wave propagating through the monitor light waveguide for the second modulation unit on the substrate. And having the first modulation unit and the second modulation unit Then, the side where the monitor light waveguide is located with respect to the output waveguide is different from each other, and the first modulation unit and the second modulation unit are arranged to be shifted from each other in the light propagation direction. Features.

(2) A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and the optical waveguide, An optical modulator comprising: a light receiving element that detects a propagating light wave; and an output for guiding the light wave modulated by the modulation unit to each of the first modulation unit and the second modulation unit. A waveguide and at least one monitor light waveguide for guiding a light wave for monitoring the modulation unit to the side of the output waveguide are provided, and the first modulation unit is used as the light receiving element. A first light receiving element for detecting a light wave propagating through the monitor light waveguide and a second light receiving element for detecting a light wave propagating through the monitor light waveguide for the second modulation unit on the substrate. Having the first light receiving element and the second receiving element. Element, while being staggered from each other in the light propagation direction, and at least a part of which is disposed so as to overlap in a direction perpendicular to the light propagation direction.

(3) A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and the optical waveguide An optical modulator comprising: a light receiving element that detects a propagating light wave; and an output for guiding the light wave modulated by the modulation unit to each of the first modulation unit and the second modulation unit. A waveguide and at least one monitor light waveguide for guiding a light wave for monitoring the modulation unit to the side of the output waveguide are provided, and the first modulation unit is used as the light receiving element. A first light receiving unit that detects a light wave propagating through the monitor light waveguide and a second light receiving unit that detects a light wave propagating through the monitor light waveguide with respect to the second modulation unit. A first light receiving portion having a light receiving element on the substrate And the second light receiving section are arranged to be shifted from each other in the light propagation direction. (4) In the optical modulator described in (3), the shared light receiving element is the first light receiving section. A light shielding structure is provided between the light receiving portion and the second light receiving portion.

(5) A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and the optical waveguide. An optical modulator comprising: a light receiving element that detects a propagating light wave; and an output for guiding the light wave modulated by the modulation unit to each of the first modulation unit and the second modulation unit. There are provided a waveguide and two monitor light waveguides for guiding light waves for monitoring the modulation unit on both sides of the output waveguide, and the monitor for the first modulation unit is used as the light receiving element. A first light receiving element including two light receiving portions that respectively detect light waves propagating through the light waveguide, and two light receiving portions that respectively detect light waves propagating through the monitor light waveguide with respect to the second modulation portion. A second light receiving element comprising: The monitor light waveguides on both sides of the output waveguide are parallelized with each other and then bent so as to increase the distance from the output waveguide. The second light receiving element is characterized in that the monitor light waveguides on both sides of the output waveguide are arranged in a section parallel to each other and are shifted from each other in the light propagation direction.
(6) In the optical modulator according to any one of (2) to (5), the first modulation unit and the second modulation unit are arranged to be shifted from each other in the light propagation direction. And

  According to the optical modulator of the present invention, it is possible to provide an optical modulator that achieves both high performance, high density, and miniaturization.

It is a top view explaining the optical modulator which concerns on the prior art example 1. FIG. It is a top view explaining the optical modulator which concerns on the prior art example 2. FIG. It is a top view explaining the optical modulator which concerns on 1st Example of this invention. It is a top view explaining the optical modulator which concerns on 2nd Example of this invention. It is a top view explaining the optical modulator which concerns on 3rd Example of this invention. It is a top view explaining the optical modulator which concerns on 4th Example of this invention. It is a top view explaining the optical modulator which concerns on 5th Example of this invention. It is a top view explaining the optical modulator which combined the 4th Example and the 5th Example.

Hereinafter, the optical modulator according to the present invention will be described in detail.
The optical modulator according to the present invention has, as a basic configuration, a substrate 1 having an electro-optic effect, an optical waveguide 2 formed on the substrate 1, and an optical waveguide 2 as shown in FIG. And a light receiving element 4 for detecting a light wave propagating through the optical waveguide 2.

The substrate 1 may be any substrate that can form an optical waveguide such as quartz or semiconductor. In particular, LiNbO ₃ (lithium niobate), LiTaO ₃ (lithium tantalate), or PLZT (zircon), which is a substrate having an electrooptic effect. A substrate using any single crystal of lead lanthanum titanate) can be suitably used.

The optical waveguide 2 formed on the substrate 1 is formed, for example, by thermally diffusing a high refractive index material such as titanium (Ti) on a LiNbO ₃ substrate (LN substrate). Further, a rib-type optical waveguide in which grooves are formed on both sides of a portion that becomes an optical waveguide and a ridge-type waveguide in which the optical waveguide portion is convex can be used. Further, the present invention can also be applied to an optical circuit in which optical waveguides are formed on different waveguide substrates such as PLC and these waveguide substrates are bonded and integrated.

The substrate 1 is provided with a control electrode 3 for controlling a light wave propagating through the optical waveguide 2 with a control signal. The control electrode 3 includes an RF electrode 3a constituting a modulation electrode, a ground electrode (not shown) surrounding the modulation electrode, and DC electrodes 3b and 3c for applying a DC signal. These control electrodes 3 can be formed by forming a Ti / Au electrode pattern on the substrate surface and using a gold plating method or the like. Furthermore, a buffer layer such as a dielectric SiO ₂ can be provided on the substrate surface after the formation of the optical waveguide, if necessary.

The optical waveguide 2 constituting the modulation section M has a structure in which a sub Mach-Zehnder type waveguide is arranged in a nest type in the arm part of the main Mach-Zehnder type waveguide. The light wave (signal light) modulated by the modulation unit M is guided to the outside of the substrate through the output waveguide 21 connected to the multiplexing unit of the main Mach-Zehnder type waveguide in the modulation unit M.
The light receiving element 4 is disposed in close proximity to the output waveguide 21, and one of the light waves of the radiated light waveguide 22 or the output waveguide 21 that guides the radiated light radiated from the multiplexing unit to the light receiving element 4. A monitoring waveguide 24 is provided for guiding the part to the light receiving element 4. The radiated light waveguide 22 guides radiated light not guided to the output waveguide 21 to the light receiving element 4 as a monitor signal. For this purpose, a radiated light guide is provided in the vicinity of a coupler structure such as an MMI (multimode interference type) coupler, an asymmetric three-branch structure, or a Y-branch structure, thereby guiding the light to the radiated light waveguide 22. be able to. The monitoring waveguide 24 distributes a part of the light wave of the output waveguide 21 as a monitor signal by the TAP coupler and guides it to the light receiving element 4.

FIG. 3 is a plan view for explaining the optical modulator according to the first embodiment of the present invention.
The optical modulator of this example includes a first modulation unit M (# 1) and a second modulation unit M (# 2) that respectively modulate light waves obtained by branching input light.
On both sides of the output waveguide 21 of each modulation section M, a radiation light waveguide 22 that propagates radiation emitted from the multiplexing section of the main Mach-Zehnder type waveguide in the modulation section M is provided. The light receiving element 4 is disposed so as to straddle the output waveguide 21 and the radiated light waveguides 22 on both sides thereof. In this example, the light receiving element 4 includes a light receiving element 4 (# 1) for the modulation unit M (# 1) and a light receiving element 4 (# 2) for the modulation unit M (# 2). Each light receiving element 4 has two light receiving portions 41 for receiving a light wave from each of the radiated light waveguides 22, and is fixed to a predetermined position on the substrate 1 with an adhesive 42. Is done. The monitor signals received by the two light receiving units 41 are electrically combined inside or outside the light receiving element. Thereby, the bias point shift between the modulation curves of the output signal and the monitor signal can be improved, and the signal strength of the monitor signal can be further increased.

The modulation unit M (# 1) and the modulation unit M (# 2) are aligned in the length direction (light propagation direction) of the substrate 1 and arranged side by side in the width direction of the substrate 1. Further, the light receiving element 4 (# 1) and the light receiving element 4 (# 2) are arranged so that the positions in the light propagation direction are shifted by one or more light receiving elements. Therefore, even if the distance between the optical waveguide 2 on the modulation unit M (# 1) side and the optical waveguide 2 on the modulation unit M (# 2) side is narrowed, the light receiving element 4 (# 1) and the light receiving element 4 (# 2) Do not overlap.
In this way, by arranging each light receiving element 4 to be shifted by one or more light receiving elements in the length direction of the substrate 1, the optical waveguide 2 on the modulation unit M (# 1) side and the modulation unit M (# 2) side are arranged. The optical waveguide 2 can be disposed close to the optical waveguide 2, and the length of the substrate 1 in the width direction (chip width W) can be shortened.

FIG. 4 is a plan view for explaining an optical modulator according to the second embodiment of the present invention.
The optical modulator according to the second embodiment is a modification of the optical modulator according to the first embodiment. In the optical modulator according to the first embodiment, the distance D21 from the start end portion (the combined portion of the Mach-Zehnder type waveguide) of the radiated light waveguide 22 to the light receiving element 4 is the same as that of the light receiving element 4 (# 1). It is different in the element 4 (# 2). In general, the distance between the radiated light waveguides 22 increases as the distance from the starting end increases, so the distance between the radiated light waveguides 22 at the position where the light receiving element 4 (# 1) is disposed and the distance between the light receiving elements 4 (# 2). The interval between the radiation waveguides 22 at the arrangement position is different. For this reason, in the optical modulator according to the first embodiment, there is a concern that a difference in the light receiving characteristics occurs between the light receiving elements 4.

  Therefore, in the optical modulator according to the second embodiment, the modulation unit M (# 1) and the modulation unit M (# 2) are arranged so as to be shifted from each other in the light propagation direction, and the light receiving element 4 (# 1) and the light receiving unit are received. The element 4 (# 2) is displaced from each other in the same light propagation direction as the direction in which the modulation unit M (# 1) and the modulation unit M (# 2) are shifted. In this example, the modulation unit M (# 1) and the light receiving element 4 (# 1) are one light receiving element downstream of the modulation unit M (# 2) and the light receiving element 4 (# 2) in the light propagation direction. They are shifted from each other. In addition, the shift amount and direction of the modulation unit M (# 1) and the modulation unit M (# 2) and the shift amount and direction of the light receiving element 4 (# 1) and the light receiving element 4 (# 2) are matched. . Therefore, the distance D21 from the start end portion (the combined portion of the Mach-Zehnder type waveguide) of the radiated light waveguide 22 to the light receiving element 4 matches between the light receiving element 4 (# 1) and the light receiving element 4 (# 2). .

As a result, the interval between the radiated light waveguides 22 at the arrangement position of the light receiving element 4 (# 1) and the interval between the radiated light waveguides 22 at the arrangement position of the light receiving element 4 (# 2) match. The light receiving characteristics can be made uniform between the light receiving elements 4. Furthermore, since the waveguide structure from the multiplexing part to the light receiving element 4 can be matched between the light receiving elements 4, the light receiving characteristics are made more uniform.
In addition, since the light receiving element 4 (# 1) and the light receiving element 4 (# 2) are shifted by one or more light receiving elements, the optical waveguide 2 on the modulation unit M (# 1) side and the modulation unit M (# 2) side are arranged. Since the optical waveguide 2 can be disposed close to the optical waveguide 2, the length in the width direction of the substrate 1 (chip width W) can be shortened.

FIG. 5 is a plan view for explaining an optical modulator according to the third embodiment of the present invention.
The optical modulator according to the third embodiment is another modification of the optical modulator according to the first embodiment.
The modulation unit M (# 1) and the modulation unit M (# 2) are aligned in the length direction (light propagation direction) of the substrate 1 and arranged side by side in the width direction of the substrate 1. In addition, the light receiving element 4 (# 1) is shifted from the light receiving element 4 (# 2) by one or more light receiving elements on the downstream side in the light propagation direction. The radiated light waveguides 22 on both sides of the output waveguide 21 are bent so as to be parallel to each other, and the light receiving element 4 is disposed in the paralleled section.

As a result, the interval between the radiated light waveguides 22 at the arrangement position of the light receiving element 4 (# 1) and the interval between the radiated light waveguides 22 at the arrangement position of the light receiving element 4 (# 2) match. The light receiving characteristics can be made uniform between the light receiving elements 4. In addition, since the light receiving element 4 (# 1) and the light receiving element 4 (# 2) are shifted by one or more light receiving elements, the optical waveguide 2 on the modulation unit M (# 1) side and the modulation unit M (# 2) side are arranged. Since the optical waveguide 2 can be disposed close to the optical waveguide 2, the length of the substrate 1 in the width direction (chip width W) can be shortened.
At the light wave output side end of the substrate 1, the output waveguide 21 does not overlap the optical axis of the signal light output from the output waveguide 21 and the radiated light output from the radiated light waveguide 22. It is desirable to bend the radiated light waveguide 22 in a direction in which the distance between the radiated light and the radiant light increases. Thereby, it can suppress that signal light (On light) and radiation light (Off light) interfere.

FIG. 6 is a plan view for explaining an optical modulator according to the fourth embodiment of the present invention.
The optical modulator of this example includes a first modulation unit M (# 1) and a second modulation unit M (# 2) that respectively modulate light waves obtained by branching input light of wavelength λ1, and input light of wavelength λ2. The third modulation unit M (# 3) and the fourth modulation unit M (# 4) that respectively modulate the respective light waves that are branched from each other. The modulators M (# 1) and M (# 2) and the modulators M (# 3) and M (# 4) are not necessarily formed on the same substrate 1 and may be formed on different substrates.
On one side of the output waveguide 21 of each modulation section M, a monitor waveguide 24 that extracts and propagates a part of the light wave propagating through the output waveguide 21 for monitoring is provided. The light receiving element 4 is disposed so as to straddle the monitoring waveguide 24. In this example, as the light receiving element 4, the light receiving element 4 (# 1) for the modulation unit M (# 1), the light receiving element 4 (# 2) for the modulation unit M (# 2), and the modulation unit M (# 3). And a light receiving element 4 (# 4) for the modulation unit M (# 4). Each light receiving element 4 has one light receiving portion 41 for receiving a light wave from the monitoring waveguide 24, and is fixed to a predetermined position on the substrate 1 with an adhesive 42.

The modulators M (# 1) to M (# 4) are arranged in the width direction of the substrate 1 by aligning the positions in the length direction (light propagation direction) of the substrate 1. The light receiving element 4 (# 1) and the light receiving element 4 (# 3) are shifted by one or more light receiving elements downstream of the light receiving element 4 (# 2) and the light receiving element 4 (# 4) in the light propagation direction. Are arranged. Therefore, even if the interval between the optical waveguide 2 on the modulation unit M (# 2) side and the optical waveguide 2 on the modulation unit M (# 3) side is narrowed, the light receiving element 4 (# 2) and the light receiving element 4 (# 3) Do not overlap.
Thus, not only between the modulation units M (# 1) and M (# 2) and between the modulation units M (# 3) and M (# 4), but also the modulation units M (# 2) and M (# 3). ), The length of the substrate 1 in the width direction (chip width W) can be shortened.

FIG. 7 is a plan view for explaining an optical modulator according to a fifth embodiment of the present invention.
The optical modulator of this example includes a first modulation unit M (# 1) and a second modulation unit M (# 2) that respectively modulate light waves obtained by branching input light.
On both sides of the output waveguide 21 of each modulation section M, a radiation light waveguide 22 that propagates radiation emitted from the multiplexing section of the main Mach-Zehnder type waveguide in the modulation section M is provided. Then, one light receiving element 4 is arranged so as to straddle the output waveguide 21 of each modulation section M and the radiated light waveguides 22 on both sides thereof. That is, in this example, one light receiving element 4 is shared by the modulation units M (# 1) and M (# 2). The light receiving element 4 has four light receiving portions 41 for receiving light waves from each of the radiated light waveguides 22, and is fixed to a predetermined position on the substrate 1 with an adhesive 42. The

  The modulation unit M (# 1) and the modulation unit M (# 2) are arranged so as to be shifted from each other in the light propagation direction. The light receiving unit 4 shared by the modulation unit M (# 1) and the modulation unit M (# 2) includes a light reception unit 41 for the modulation unit M (# 1) and a light reception unit 41 for the modulation unit M (# 2). , The modulation unit M (# 1) and the modulation unit M (# 2) are shifted from each other in the same light propagation direction. In this example, the shift amount and direction of the modulation unit M (# 1) and the modulation unit M (# 2), the light receiving unit 41 for the modulation unit M (# 1), and the light receiving unit 41 for the modulation unit M (# 2). The shift amount and direction are matched. Accordingly, the distance D22 from the light-receiving element 4 (# 1) and the light-receiving element 4 (# 2) is equal to the distance D22 from the start end of the radiated light waveguide 22 (the combined part of the Mach-Zehnder waveguide) to the light-receiving part 41 .

  Thus, the number of components on the substrate 1 can be reduced by sharing one light receiving element 4 between the modulation unit M (# 1) and the modulation unit M (# 2). Further, since the optical waveguide 2 on the modulation unit M (# 1) side and the optical waveguide 2 on the modulation unit M (# 2) side can be arranged close to each other, the length in the width direction of the substrate 1 (chip width W) is shortened. it can. Furthermore, since the arrangement of the light receiving portions 41 in the light receiving element 41 is matched to the shifting method of the modulation portions M (# 1) and M (# 2), the light receiving characteristics can be made uniform between the light receiving portions 41.

  The configuration of the fifth embodiment can be used in combination with the configurations of other embodiments. For example, as shown in FIG. 8, an optical modulator combined with the configuration of the fourth embodiment may share one light receiving element 4 in a modulation unit that modulates light waves having different wavelengths. In FIG. 8, the light receiving element 4 (# 2, # 3) shared by the modulation unit M (# 2) for the light wave having the wavelength of λ1 and the modulation unit M (# 3) for the light wave of the wavelength of λ2 is provided. In this shared light receiving element 4 (# 2, # 3), it is desirable to provide a light blocking structure 43 for preventing signal mixing between monitor signals between the light receiving sections 41 for the respective modulation sections. As the light shielding structure 43, for example, an embedded electrode or a groove structure can be used.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above-described contents, and it is needless to say that the design can be changed as appropriate without departing from the gist of the present invention.

  As described above, according to the present invention, an optical modulator having a light receiving element for each of a plurality of modulation units can be provided with a reduced chip width.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Optical waveguide 3 Control electrode 3a RF electrode 3b, 3c DC electrode 4 Light receiving element 21 Output waveguide 22 Radiated light waveguide 24 Monitor waveguide 41 Light receiving part 42 Adhesive 43 Light shielding structure

Claims (6)

A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and an optical wave propagating through the optical waveguide A light modulator comprising: a light receiving element for detecting
For each of the first modulation unit and the second modulation unit, an output waveguide for guiding the light wave modulated by the modulation unit and a light wave for monitoring the modulation unit are provided for the output. At least one waveguide for monitoring light guided to the side of the waveguide,
As the light receiving element, a first light receiving element that detects a light wave propagating through the monitor light waveguide with respect to the first modulation unit and a light wave that propagates through the monitor light waveguide with respect to the second modulation unit are detected. A second light receiving element on the substrate;
The first modulation unit and the second modulation unit are different from each other on the side where the monitor light waveguide is located with respect to the output waveguide.
The optical modulator, wherein the first modulation unit and the second modulation unit are arranged to be shifted from each other in the light propagation direction. A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and an optical wave propagating through the optical waveguide A light modulator comprising: a light receiving element for detecting
For each of the first modulation unit and the second modulation unit, an output waveguide for guiding the light wave modulated by the modulation unit and a light wave for monitoring the modulation unit are provided for the output. At least one waveguide for monitoring light guided to the side of the waveguide,
As the light receiving element, a first light receiving element that detects a light wave propagating through the monitor light waveguide with respect to the first modulation unit and a light wave that propagates through the monitor light waveguide with respect to the second modulation unit are detected. A second light receiving element on the substrate;
The first light receiving element and the second light receiving element are disposed so as to be shifted from each other in the light propagation direction, and are disposed so as to overlap at least partially in a direction orthogonal to the light propagation direction. Light modulator. A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and an optical wave propagating through the optical waveguide A light modulator comprising: a light receiving element for detecting
For each of the first modulation unit and the second modulation unit, an output waveguide for guiding the light wave modulated by the modulation unit and a light wave for monitoring the modulation unit are provided for the output. At least one waveguide for monitoring light guided to the side of the waveguide,
As the light receiving element, a first light receiving unit that detects a light wave propagating through the monitor light waveguide with respect to the first modulation unit, and a light wave that propagates through the monitor light waveguide with respect to the second modulation unit are detected. A common light-receiving element including a second light-receiving unit on the substrate;
The optical modulator, wherein the first light receiving unit and the second light receiving unit are arranged to be shifted from each other in the light propagation direction. The optical modulator according to claim 3.
The shared light receiving element has a light shielding structure between the first light receiving unit and the second light receiving unit. A substrate having an electro-optic effect, an optical waveguide formed on the substrate, a first modulation unit and a second modulation unit that modulate light waves propagating through the optical waveguide, and an optical wave propagating through the optical waveguide A light modulator comprising: a light receiving element for detecting
For each of the first modulation unit and the second modulation unit, an output waveguide for guiding the light wave modulated by the modulation unit and a light wave for monitoring the modulation unit are provided for the output. Two monitor light waveguides guided on both sides of the waveguide,
As the light receiving element, a first light receiving element provided with two light receiving parts for detecting light waves propagating through the monitor light waveguide for the first modulation part, and a monitor light guide for the second modulation part, respectively. A second light receiving element having two light receiving portions for detecting light waves propagating through the waveguide, respectively, on the substrate;
The monitor light waveguides on both sides of the output waveguide are made parallel to each other, and then bent so as to increase the distance from the output waveguide.
The first light receiving element and the second light receiving element are disposed in a section where the monitor light waveguides on both sides of the output waveguide are parallel to each other, and are shifted from each other in the light propagation direction. An optical modulator characterized by that. The optical modulator according to any one of claims 2 to 5,
The optical modulator, wherein the first modulation unit and the second modulation unit are arranged to be shifted from each other in the light propagation direction.

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